The present invention relates generally to bicycles and, in particular, to the clamping means for mounting a saddle or seat on the seat post of a bicycle frame.
The saddle or seat for bicycles is removably mounted on the upper end of a seat post which is fitted to the seat tube of a bicycle frame and fixed thereto at an adjustable height The angle of the seat post with respect to vertical may be slightly different from bicycle to bicycle according to the design, but it is required that the seat be fixed in place at an adjusted angle so that the seat top will be approximately horizontal irrespective of the angle of the seat post and further that the seat be angularly adjustable so as to incline the seat top downward and upward as desired by the rider.
To fulfill the adjustability requirement, the seat post is usually provided with an adjustable clamping mechanism for mounting of the bicycle seat. The bicycle seat typically has two longitudinally extending wires which are clamped to the seat post by the clamping mechanism. In the prior art, there are three primary types of clamping mechanisms used to secure the wires or saddle rails of a bicycle seat. One type of clamping mechanism used one bolt to hold and clamp the assembly. Such a mechanism is shown in the U.S. Pat. No. 3,992,054. The U.S. Pat. No. 4,275,922 shows another type of clamping mechanism using two bolts, a primary clamping bolt to clamp the assembly and a second bolt to adjust or hold the primary adjustment socket. A second type of two bolt mechanism has two bolts acting in teetertotter fashion to perform the adjustment and clamping functions as shown in the U.S. Pat. No. 3,891,333.
In the prior art, the base or cradle plate in the clamping mechanism is metal and typically has been made by stamping, casting, or forging. The more recent prior art has included the use of extruded metal components. Although the use of extruded metal components was more efficient from a manufacturing standpoint, performance problems have occurred due to the fact that the necessary tolerances to achieve the desired fit of the upper end of the post and the socket in the base of the clamping mechanism are difficult to maintain. An improper or loose fit may result in transverse shifting of the clamping mechanism and seat on the seat post.
The design of the present invention eliminates transverse shifting of the clamping mechanism. Diametrically opposed chamfered edges on the upper end of the seat post engage surfaces of the downwardly and outwardly extending side walls of a longitudinally extending slot formed in the lower cradle member of the clamping mechanism. This creates two approximately equal and opposing surface areas of engagement between the seat post and the clamping mechanism to prevent transverse shifting of the clamping mechanism and the seat without restricting the forward and rearward tilt adjustment of the seat.